1. Field of the Invention
The present invention relates to valves for internal combustion engines and more particularly to spherical valves for transferring gasses to and from individual combustion chambers in internal combustion engines.
2. Discussion of the Related Art
Internal combustion engines require a valving system to deliver fuel-air mixtures to and to remove combustion gasses from individual combustion chambers in the engine. The majority of internal combustion engines in operation incorporate a valving system based on variations of a spring-loaded poppet valve wherein the spring normally biases the valve in a closed position. In the closed position, the head of the valve is seated against either an intake port or an exhaust port in each individual cylinder head. The valves themselves are usually positioned in the cylinder heads such that they normally operate in a substantially vertical orientation. A valve stem extends from the top of the valve through a guide in the cylinder head to contact a camshaft or alternatively, a rocker arm which in turn contacts the camshaft. The camshaft, in turn, is mechanically linked to and driven by the engine.
In operation, as the engine rotates, the camshaft is likewise rotated such that the individual cams on the camshaft operate on the valve stems either directly or through the linked rocker arms. As each valve is operated on by the camshaft, the normal bias of the spring is overcome to push the valve head into the individual combustion chambers of the engine thereby opening either an intake port or an exhaust port to permit transfer of intake or exhaust gasses. The valves must be pushed axially a sufficient distance and remain open for a sufficient time to permit the desired volume of gas to enter or be expelled from the cylinder.
Poppet valves have significant disadvantages. In some engines, to obtain the desired flow of intake or exhaust gasses, the valve heads in their extended open position extend below the extreme upward or top dead center of the piston. Thus, timing of the valve operation has distinct limitations and becomes critical to prevent the piston from striking the valve head in its open position and causing extensive damage to the engine.
Poppet valve configurations have an extensive collection of hardware and components to complete the assembly and operation of the valving system. These items include springs, cotters, guides, rockers, camshafts, pushrods, lifters, and the valves themselves. Many internal combustion engines now incorporate multiple valve systems wherein there is more than one intake valve per cylinder and more than one exhaust valve per cylinder thereby increasing the complexity and number of individual parts attributable to the valve system. Additionally, some engines also incorporate multiple camshafts. The number and complexity of the valve system components increases the cost of the engine and the cost of repair.
In conventional internal combustion engines the spring biasing the poppet valve in its closed position is relatively stiff to insure the closing and seating of the valve head at the desired time. Therefore, the force required to overcome the spring to open the valve is quite large and correspondingly reduces the efficiency of the engine. The stiffness of the spring may also limit the timing events of the engine and thus further limit its efficiency and performance. Additionally, at high speeds an engine can experience valve float. Valve float occurs when the engine speed exceeds the ability of the valve spring to close the valve prior to the completion of the intake or exhaust stroke thereby causing engine power to diminish.
Yet another disadvantage of using conventional poppet valves is that even in the open position, the valve partially obstructs the port through which the gasses flow. Additionally, the valve head is directly below the port and thus the gas must flow around the valve head rather than flow directly into or out of the combustion chamber. This is especially critical for the intake valve since the obstruction of the valve head can cause turbulence and dead spaces within the cylinder thereby decreasing the combustion efficiency and thereby engine efficiency.
Thus what is desired is a valve system for internal combustion engines that reduces the number and complexity of parts, and does not restrict or disrupt the flow of gasses into or out of the combustion chambers of the engine.